Efficient Resource Usage For Location Sharing In Computer Networks

ABSTRACT

A location sharing system and related processes across computer networks are provided that efficiently utilize resources by adjusting location determination techniques at client devices. A rule-based architecture including user-based heuristics facilitates location determination that is accurate while optimizing resource consumption. Current interest in or other behavior associated with a target user or requesting user can be used in selecting a location determination protocol at the client device. An accurate portrayal of a user&#39;s location can be provided efficiently by correlating interest to utilize more accurate but larger resource-intensive components when interest is higher and to utilize less accurate but lower resource-intensive components when interest is lower.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 14/464,530, entitled “Efficient Resource Usage For LocationSharing In Computer Networks,” by Laws, et al., filed Aug. 20, 2014,which is a continuation of U.S. patent application Ser. No. 13/527,472,entitled “Efficient Resource Usage For Location Sharing In ComputerNetworks,” by Laws, et al., filed Jun. 19, 2012, now U.S. Pat. No.8,831,632, which claims priority from U.S. Provisional PatentApplication No. 61/651,983, entitled “Efficient Resource Usage ForLocation Sharing In Computer Networks,” by Laws, et al., filed May 25,2012, all of which are incorporated by reference herein in theirentirety.

BACKGROUND

Embodiments in accordance with the present disclosure relate to computernetworks, and more particularly to location sharing between computingdevices in computer networks.

Many computing devices use location determination to providelocation-based services. For example, many devices offer turn-by-turndirections, mapping of nearby points of interest and landmarks, targetedemergency assistance, and location sharing services. Various locationdetermination mechanisms are typically available to mobile devices. Forexample, a device may include a cellular location service that utilizescellular information such as the strength of signal from one or morecellular antennas to determine device location using the known locationof the antenna. A device may also utilize other network connections,such as a wireless (e.g, Wi-Fi) or wired connection to determine itslocation using the known location of the wireless network antenna orwired network connection. Satellite-based positioning technology, for aGlobal Positioning System (GPS) for example, is also included on manydevices.

Many mobile devices supplement GPS with technologies such as Time ofArrival (TOA), Enhanced Cell Identification, and Assisted GlobalPositioning System (A-GPS). For example, A-GPS uses a combination of GPSsatellites and cellular network base stations to more accurately and/ormore rapidly pinpoint the location of a GPS receiver associated with amobile device.

Accessing location determination technology by a mobile device mayconsume a large amount of onboard resources. In situations where adevice is used for other traditional features, such as cellular voicefeatures, email and other messaging applications, internet browsers,games, music, etc., application usage of geo-positioning systems mayconsume an unacceptable level of resources, for example by consuming anundesirable level of battery power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting components of a location sharingsystem in accordance with one embodiment.

FIG. 2 is a block diagram of a client device including a locationsharing engine in accordance with one embodiment.

FIG. 3 is a flowchart describing a process of location sharing betweenclient devices in accordance with one embodiment.

FIG. 4 is a flowchart describing a process at a location sharingplatform for location sharing between client devices in accordance withone embodiment.

FIG. 5 is a flowchart describing a process at a client device forswitching between location determination protocols in accordance withone embodiment.

FIG. 6 is a flowchart describing different location determinationprotocol processing at client devices in accordance with one embodiment.

FIG. 7 is a simplified block diagram of a computing device that can beused to implement various embodiments of the disclosed technology.

DETAILED DESCRIPTION

A location sharing system for computer networks is provided thatfacilitates an accurate determination of computing device location whileefficiently utilizing the onboard resources of the device. Thedetermination of device location can be influenced or selected based onuser behavior associated with a user of the device, as well as thebehavior associated with users of other devices. User behavior canprovide an indication of interest in a target user or device, andthereby be integrated into location determination to avoid unnecessaryconsumption of resources such as battery power for a mobile clientdevice. If the system determines that interest exists for a particularuser at a current time for example, a client device associated with theuser can be set to a high-accuracy location determination protocol modeto match the interest of other users of the system. If the systemdetermines that interest is less for the particular user, the associatedclient device can be set to a low-accuracy location determinationprotocol mode. Other factors, characteristics, and information can beused to switch client devices between different location determinationprotocols in the system.

In accordance with one embodiment of the presently disclosed technology,a client device includes at least two position determination mechanisms.For example, the client device may include a network-based locationdetermination mechanism that utilizes cellular connections or othernetwork (e.g., LAN, WAN) connections to determine a location of theclient device. The device may also include a satellite-based locationdetermination mechanism such as a global positioning system (GPS) todetermine a location of the client device. The location sharing systemmay switch the client device between the network location protocol andthe satellite location protocol based on interest of other users in thelocation of the client device or subscriber associated with the clientdevice. In this manner, a more accurate location as determined from thesatellite protocol can be used when there is interest in the location ofa device and a less accurate location as determined from the networkprotocol can be used when there is no or less interest in the locationof the device. This may facilitate less power consumption by using thenetwork protocol when there is no or less interest in the location ofthe device.

In one embodiment, heuristics of user behavior are used in selecting alocation determination protocol. For example, the system may determinefrom a first user's interaction with a first client device, anindication of interest in a second user at a second client device. Thesystem may determine that the first client device has displayed orotherwise utilized a location of the second user (e.g., on a map orother application). The system may further examine the behavior of thefirst user based on their interaction with the first client device, forexample to determine locations of the first client device that indicatethat the first user is moving closer to the second user. The system mayfurther determine a state of the second user, such as whether the seconduser is actively utilizing the location sharing system or a state of thesecond client device. Based on heuristics that indicate the first useris interested in the second user and is moving toward the second user,the system may set the second client device into a higher accuracylocation determination protocol if not already in a high accuracy mode.

In one embodiment, the first client device includes a location sharingengine that generates location information for the first client deviceas well as tracking information relating to other users for whom thefirst user has indicated location interest. A location sharing platformincluding a processor-based server receives the location information andthe tracking information. The platform determines that the trackinginformation indicates interest in the second user and that the seconduser is associated with the second client device. The platform providesthe tracking information to the second client device indicating interestin the location of the second client device. A location sharing engineat the second client device can utilize the information to determinewhether a location determination protocol at the second client deviceshould be changed to determine and report location to the locationsharing platform. In one embodiment, the platform may determine that theprotocol at a particular client device should be changed and issue aninstruction to the device in place of or in addition to the information.

In one embodiment, the tracking information or an instruction can besent directly from the first client device to the second client devicewithout utilizing the location sharing platform. For example, the firstclient device can send information indicating an interest in thelocation of the second client device directly to the second clientdevice. The second client device can use the information to place thelocation sharing engine into an appropriate location determinationprotocol. In one embodiment, the second client device may periodicallypoll the first client device or the location sharing platform todetermine tracking information or other indication of interest. Thesecond client device may alternatively receive instructions orinformation using a push protocol to wake up or activate the secondclient device and/or location sharing engine at the second clientdevice. The instruction or information can come from either the firstclient device directly or from the location sharing platform. Thelocation sharing engine can then determine an appropriate locationdetermination protocol.

FIG. 1 is a block diagram of components that can be used to implement alocation sharing system between client devices over computer networks inaccordance with one embodiment. A location sharing platform (LSP) 102,client devices 104 and a remote location processor 106 are incommunication with one or more computer networks 110. Although twoclient devices and a single remote location processor are depicted, anynumber of client devices and remote location processors may be includedin various implementations. More or fewer than the components may beincluded in other embodiments.

Network(s) 110 can include any combination of local area networks, widearea networks (WAN), the Internet, and/or any other network. As will bedescribed with respect to specific embodiments hereinafter, network 110typically includes at least one public network such as the Internet withthe various components communicating using well know communicationprotocols such as HTTP, HTTPs, etc. The various resource requests andmessages as described herein can be transmitted using any number ofwell-known communication and network protocols. They can include apacket, cell, message, or signal used to ask for and receive resources.Some examples include the HTTP communication protocol over a TCP/IPnetwork protocol, HTTPS over SSL, FTP, etc.

Client devices 104 may generally include any type of device such as apersonal computer, tablet, PDA, cell phone, or other processor-basedcomputing device. Typically, the client devices will be mobile devicesbut in some cases a non-mobile client device may be used, such as toinquire as to the location of other users or as an update to a user'scurrent location at a non-mobile device. In many examples, the mobiledevices are integrated with receiver/transmitter technology so that theycan send and receive telephone calls or other messages via a network.Mobile devices include cellular telephones, palmtops, pocket computers,personal digital assistants, personal organizers, personal computers(PCs), and the like. Although described herein in combination withclient devices 104, alternative embodiments can be used with any numberof computer systems, such as desktop computers, other hand-held devices,laptop or notebook computer systems, multiprocessor systems,micro-processor based or programmable consumer electronics, network PCs,mini computers, main frame computers and the like. Reference to mobiledevices is made hereinafter by example but it will be understood toinclude reference to other devices except where noted.

In FIG. 1, mobile devices 104 are in communication with a transceiver114 such as an antenna provided a telecommunications operator that mayprovide services to both fixed and mobile devices. Operator systems canprovide access to networks 110 through operator mobile and IP networks,for example. Such systems may include an interface network (IN) server,an OMA server, and a cloud server, for example.

In various embodiments, client devices 104 may include position orlocation determination functionality. For example, devices 104 mayutilize a cellular network-based location determination protocol todetermine location using cellular network ground station antennas. Theymay also utilize wired or wireless network connections to determinelocation using known locations of networks or network access points.Distance to an antenna, strength of signal, etc. from/to an antenna maybe used to determine a position or location based on a known position ofthe antenna. The location determination may be done locally by theclient device, remotely or using a combination of these techniques. Anoptional remote location processor 106 is depicted, which may receiveinformation indicating a cell tower connection and determine a device'slocation. This information may be provided back to the mobile device orto platform. In other examples, the remote location processor mayprovide information to the client device from which it can determinelocation. Generally, cellular location protocols provide about a 500meter to 1,500 meter accuracy and consume a large amount of batterypower. Wi-fi connection protocols, for example, provide about a 50 meterto 200 meter accuracy and consume much less battery power than cellularnetwork protocols.

Mobile devices 104 are also in communication with one or more satellites116 and optionally, one or more ground station terminals (not shown).Mobile devices 104 may include on-board circuitry and/or software forcommunicating (uni-directional or bi-directional) with thegeo-positioning satellites 116 for location determination. The on-boardcircuitry, such as a GPS processor and transceiver, may be configured toreceive satellite data and to calculate position or location using thedata. The mobile devices may operate in any of these modes independentlyor in combination with each other. For example, in an A-GPS mode themobile device can use cellular connection information and satellite datato determine location. Satellite location protocols generally offer 5meter to 15 meter, or even better, accuracy, but consume a larger amountof battery power than that consumed by most cellular location protocols.

Location sharing platform 102 includes one or more web servers 122 andone or more application servers 124 for providing location sharingservices to mobile devices 104 over networks 110. Application server 124implements a location manager 130 that receives and processesinformation from mobile devices 104 and/or remote location processors106 to provide location-based information to the mobile devices. Webserver 122 provides a web-based interface to mobile devices 104, such asby using standard HTTP or HTTPs protocols, although any suitablecommunication protocol may be used. In one example, the web serverprovides a graphical user interface. In other examples, the web serverprovides a communication interface without a graphical component.

Location manager 130 is in communication with a registration database132 that stores subscriber account information, such as account names,passwords, preferences, permissions, characteristics and otherinformation of the user. Data structures and objects or other techniquescan be used to manage information relating to the subscribers or usersof the location sharing system. In one example, the users of the mobiledevices form a group or other set of individual users who desire tointeract and share location information. A user may set a preference tobe supplied with location information for a particular user. The usermay set a permission to allow another user to view their locationinformation. Through these preferences and permissions, social or othergroups can be defined and enable location sharing between users in thegroup. Each parameter or characteristic for each user is stored in theregistration database.

Map database 134 may store one or maps to provide a map platform overwhich location information may be displayed using position informationas described herein. In one embodiment, the map database providesbackground maps or images that can be provided to and displayed onclient devices 104. Various maps may be included so that differentviews, for example corresponding region around the viewing user oraround a target user can be provided. Map tiles including image fileswith different granularity levels are used in one example. This mayfacilitate views at world, continent, region, country, street, etc. Themaps may be stored locally or remotely in a map database 134, and beprovided by the platform 102 to the appropriate mobile device 104. Thirdparty map providers may also be used.

Location database 136 stores position or location information for thesubscribers of location sharing services. Location information mayinclude, but is not limited to, latitude, longitude, current location,altitude, position fix information, sector-based position location,position uncertainty information, device orientation, headinginformation, velocity (horizontal and/or vertical vector). Trackingdatabase 138 stores tracking information describing the relationshipsbetween users, such as who a particular user is tracking and the statusof the user and current interest level in the other user. The trackinginformation may include an identification of users a user is currentlytracking. This information may include the user's identification andoptionally additional information. For example, the tracking informationmay include a level of interest in the target user at that time, howaccurate a position is being requested for the target user, etc. Byincluding tracking information that indicates interest in the users byother users at a current time, the location sharing system mayefficiently determine location information while minimizing powerconsumption by the client devices.

Although databases are used for data storage in FIG. 1 other datastorage techniques may be used. For example, the information may bemaintained in flat files or other data structures, includingunstructured schema-defined data. Embodiments may also be practiced indistributed computing environments where tasks are performed by remoteprocessing devices that are linked through a communications network in adistributed computing environment, with programs located in both localand remote memory storage devices. Although specific components andsoftware modules are depicted, it will be apparent that numerousphysical and software based configurations may be employed whileremaining within the spirit of the present disclosure. Generally,software and program modules as described herein include routines,programs, components, data structures, and other types of structuresthat perform particular tasks or implement particular abstract datatypes. Hardware or combinations of hardware and software can besubstituted for software modules as described herein.

It is noted that embodiments can be implemented within the clientdevices 104 without a location sharing platform 102. For example, clientdevices 104 can communicate with another to pass tracking and locationinformation directly without using the LSP 102.

FIG. 2 is a block diagram of an example of a mobile device 104 that canbe used to implement embodiments of the disclosed technology. Typicalelectronic circuitry is described with a location sharing system fordetermining location information, receiving location information fromlocation sharing platform 102, and providing location information to LSP102. Mobile device 104 can be used to implement a phone such as a smartphone or other device that can run one or more applications such as, forexample, browser, email, scheduling, instant messaging, and media playerapplications.

Mobile device 104 includes control circuitry 202, memory 220, display204 and I/O device(s) 206 connected to one or more data buses (notshown). A peripheral device port 208 is provided for connecting tovarious peripherals. The control circuitry 202 includes one or moremicroprocessors. Memory 220 typically includes both non-volatile memorysuch as ROM and volatile memory such as RAM. Memory 220 storesprocessor-readable code which is executed by one or more processors ofthe control circuitry 202 to implement various functionality describedherein. I/O device(s) 206 may include any number of input/outputdevices, such as a rollerball, push button numeric dialing pad, etc. Inone example, a separate I/O device may not be included in the mobilecomputing device such as where a touch screen or stylus is used. Powersupply 216, which can include one or more batteries and/or an externalpower source, powers the various components of the mobile device. In oneexample, a mobile device 104 is a cell phone, personal digitalassistant, handheld computer, or the like including a touch screendisplay and input buttons to allow the user to enter information intothe mobile device. In other embodiments, the mobile device mayincorporate more or fewer input elements, for example, the display maynot be a touch screen in some embodiments. The mobile device may alsoinclude a keypad, such as a physical keypad or a “soft” keypad generatedon the touch screen display.

The control circuitry further communicates with audio interface 212 andvideo interface 214. Audio interface 212 may be used with a speaker toprovide audible signals to a user and a microphone to receive audiblesignals from the user, such as to facilitate a telephone conversation.Video interface 214 enables operation of an on-board camera to recordstill images, video streams, and the like, and further enables video fordisplay 204.

Operating system 242 is resident in memory 220 and executes on controlcircuitry 202. Various operating systems can be used. By way ofnon-limiting example, the operating system may iOS from Apple, Inc.,Blackberry OS from RIM, Inc. or Windows Mobile OS from Microsoft. One ormore applications 242 are loaded into memory 220 and run on or outsideof the operating system. Examples of application programs include phonedialer programs, e-mail programs, PIM (personal information management)programs, word processing programs, spreadsheet programs, Internetbrowser programs, and so forth.

The control circuitry 202 communicates with cellular transceiver 250which in turn is coupled to an antenna (not shown) to transmit andreceive radio frequency communications. The control circuitry controlstransmission and reception of wireless signals. During a transmissionmode, the control circuitry 310 can provide a voice signal or datasignal to the transmit/receive circuitry of the cellular transceiver.The transmit/receive circuitry transmits the signal to a remote station(e.g., a fixed station, operator, other cellular phones, etc.) forcommunication through the antenna. Transmissions to and from thecellular transceiver 250 can be conducted under control of the operatingsystem 240. Communications received by the cellular transceiver may bedisseminated to applications 242 via the operating system 240, and viceversa. During a receiving mode, the transmit/receive circuitry receivesa voice or other data signal from a remote station through the antenna.A received voice signal is provided to the speaker while other receiveddata signals are also processed appropriately.

Additional RF transceivers 252 can interface with control circuitry 202to facilitate communications with external systems such as intranets,network databases, network storage systems, cellular networks, locationservers, presence servers, Voice over Internet Protocol (VoIP) networks,local area networks (LANs), wide area networks (WANs), metropolitan areanetworks (MANs), personal area networks (PANs), and other networks.

Satellite position system (SPS) circuitry 254 may implement one or moresatellite-based location determination techniques. For example, the SPScircuitry may implement GPS or A-GPS technologies in one example,although other types of satellite-based location determinationtechnologies may be used. In one example, the SPS circuitry mayimplement a GPS engine to provide location determination capabilitiesfor the mobile device. The position engine may be implemented ashardware, software or software operating with hardware (e.g, a GPSreceiver) to receive and process satellite signal for locationdetermination.

Position engine 230 interfaces with SPS circuitry 254, cellulartransceiver 250 and/or additional RF transceivers 252 for determining alocation of mobile device 104. Position engine 230 may access the SPScircuitry which receives signals from SGS satellites 116 to determine alocation of the mobile device using GPS or AGPS protocols. The positionengine 230 may also access any of the RF transceivers to interface withcellular network based systems (transceiver 232), including nodes,location transmitters and/or beacons, wireless network transmitters andreceivers (transceivers 234), combinations thereof, and the like. Withtransceivers 250 and 252, the position engine 230 may use techniquessuch as cell global identity (CGI) with our without timing advance,enhanced forward link trilateration (EFLT), time different of arrivaltechniques (TDOA), and the like to determine the mobile device'slocation. The position engine 230 may further access one or more remotelocation processors 106 using one of the transceivers to determine alocation of the mobile device from or using information provided by theremote location processors.

Location sharing engine (LSE) 232 facilitates location determination andsharing between the local client device and one or more other clientdevices. In one embodiment, LSE 232 receives location information fromthe location sharing platform (LSP) for one or more of the other clientdevices or directly from the client devices. The location information ofthe other client devices can be stored locally in location database 234in one embodiment, along with user information associated with thosedevices. The stored information can include a history of locations inone example, to facilitate tracking or other processing. In otherexamples, the LSE 232 can maintain this information in main memorywithout using database 234.

LSE 232 facilitates the use of the location information, for example, bydisplaying the location information at the client device or providingthe information to other applications 242 through an applicationprogramming interface of the LSE 232. In one embodiment, LSE 232interfaces with a map database 236 that can provide background, image orother maps over which can be displayed the location of the local mobiledevice or any number of remote mobile devices. In one embodiment, themaps are not stored locally but are provided by the LSP 102 or athird-party provider.

LSE 232 generates tracking information to indicate any remote users thelocal user is tracking. For convenience, the terms local user (device)and remote user (device) are used to differentiate between a local useror device generating tracking information relating to one or more users,and the remote users or devices indicated in the tracking information.

In one embodiment, the tracking information is generated by determiningwhich users have a location currently within a display view provided bythe LSE. LSE 232 may make other determinations as well, such as a levelof interest in a particular user. This may be based, for example, onwhether the subscriber has actively selected that user on the display orwhether the subscriber has provided other information indicatinginterest, such as by determining that the subscriber has adjusted thedisplay so that particular user remains in view. LSE 244 provides thetracking information to LSP 102 for use by the location manager ordirectly to one or more of the other appropriate client devices.

LSE 232 also interfaces with the position engine 230 to receive locationinformation for the mobile device 104 and to provide that information toLSP 102 or the mobile devices 104 of other users. LSE 232 implements arule-based architecture for how the location of the local mobile deviceis determined. This architecture addresses resource consumption forlocation determination by utilizing different location determinationtechniques based on user behavior. In one embodiment, the locationdetermination technique may be based on the user behavior of the localmobile device. In another embodiment, however, the locationdetermination technique for the local mobile device is based on userbehavior associated with a remote mobile device. For example, theinterest of other subscribers in the user of the local mobile device atdifferent times may be used to change the mode of location determinationin an effort to balance resource consumption with the relative interestin the local subscriber. LSP 102 may acquire and provide trackinginformation and/or location information from a remote mobile device tothe local mobile device or the local mobile device may receive theinformation directly. The LSE 244 can use the tracking information todetermine a level of accuracy or mode of location determination for thelocal mobile device. In another example, the LSP 102 can provide aninstruction to the LSE 244 of a mobile device to use a particular modeof location determination or to provide a particular level of accuracyof location information. In another embodiment the instruction may comedirectly from another client device.

FIG. 3 is a flowchart describing a method performed by a locationsharing system in accordance with one embodiment. At step 302, thelocation sharing system receives subscriber information and associatesthe subscriber with one or more client devices. Step 302 may includereceiving account information such as a username and password for a userand identification information for one or more client devices associatedwith the user. The system may also receive preferences such as privacysettings or privilege information for the user. The user information maybe used to create a user profile.

At step 304, the location sharing system receives connection and sharinginformation from the subscriber. Connection information includes anidentification of one or more users the subscriber wishes to track orfrom whom the subscriber would otherwise like to obtain locationinformation. The sharing information includes an identification of oneor more users with whom the subscriber would like to share theirlocation information. The sharing information may be further partitionedto permit the subscriber to provide different forms or levels oflocation sharing to different users. For example, the subscriber mayspecific a level of accuracy or radius of location to share withdifferent users. For instance, the subscriber may specify lower levelsof accuracy, such as regional, city, street, or other area for certainusers to control the amount of information that is shared. Variousprivacy and control settings may be provided.

It is noted that steps 302 and 304 may be performed at any time and thatuser, connection and sharing information may be updated or generatedcontinuously or at initiated intervals. For example, a user may viewanother user from with a display provided by LSE 244 or anotherapplication and select to follow or otherwise track that user'slocation, thereby updating the connection and/or sharing information.

At step 306, current location and tracking information is received fromthe users' client devices. Like steps 302 and 304, the locationinformation and tracking information may be received at any time at step306. The location information indicates the current location (or ahistory of locations) of a particular (local) client device and thetracking information indicates any remote users or devices being trackedat the local client device. The tracking information may take variousforms, for example, simply indicating which remote users locationinformation is being used at the local mobile device. The indication maybe of which users' locations are currently within a field of view on thedisplay of the local mobile device. The indication may further provideinformation relating to a level of interest in each user. For example,if the user is displayed on a map at a street or city level, theindication may be of a high or relatively high interest in the user. Ifthe map is at a regional or country level, however, the indication maybe a relatively low interest.

At step 308, the location sharing system correlates the trackinginformation from each client device with the location informationreceived or already stored in location database 136. The locationinformation is used to generate messages to each mobile device based onthe tracking information for that mobile device. In one example, thesystem accesses a database of available location information for eachmobile device corresponding to the tracking information for a requestingmobile device. The system generates a message for the requesting mobiledevice with the available location information corresponding to eachuser being tracked at the requesting mobile device as indicated by thetracking information. The information and/or messages may be sent usinga location sharing platform or directly between the client devices.

At step 310, the location sharing system initiates locationdetermination protocol changes at the mobile devices based on thecorrelation of tracking information with location information at step308. For example, the system can adjust the level of accuracy at aparticular mobile device based on the tracking information received fromanother mobile device. The tracking information received from a firstmobile device may indicate that location information for a userassociated with a second mobile device is being used at the first mobiledevice or is being requested by the first mobile device. The LSP, forexample, can access the available location information for the secondmobile device to determine if any changes to the location determinationprotocol at the second mobile device are needed. In another example, thesecond mobile device can initiate a change in protocol based on trackinginformation it receives from the LSP or directly from another mobiledevice indicating an interest in the location of the second mobiledevice.

At step 312, location information is distributed to requesting mobiledevices in accordance with the correlation and messages generated atstep 308. In one embodiment, a requesting mobile device issues a requestto the LSP for location information in the form of the trackinginformation received at step 306. The LSP can access a database storinglocation information for each device corresponding to a user indicatedin the requesting device's tracking information. The LSP can generate aresponse with all available location information. Other information maybe passed at step 312 as well, such as profile information for the userswhose location information is being transmitted. In one example, the LSPmay return an indication for any location information that is notavailable. The LSP may also return an indication of how old or how muchtime has elapsed since the device's location was updated. The local LSEcan indicate on the display of the local mobile device that the locationdata is old or should be considered unreliable. In one embodiment thelocation information is distributed directly without using an LSP.

FIG. 4 is a flowchart describing one embodiment of using trackinginformation and location information to facilitate location sharing. Inone example, the process of FIG. 4 can be performed at step 308 of FIG.3 by LSP 102. At step 350, the location manager 130 accesses locationinformation and tracking information associated with a first user. Step350 can be performed at a periodic interval or be triggered by variousevents. In one example, step 350 begins in response to receiving amessage from a client device associated with the first user. The messagemay include location information for the client device and trackinginformation indicating one or more remote users for which the first userwishes to obtain location information. In one example, the message is anHTTP request packet including the location and tracking information. Thelocation information and tracking information can be stored in databases136 and 138, respectively.

At step 352, the location information for the users indicated in thefirst user's tracking information is accessed. Step 352 can includeaccessing the location database to determine the location informationfor each of the remote users. The location manager may also access anyinformation indicating when the location information for a correspondinguser was received and what the quality of the location information is.The LSE may also access any profile information or other informationmaintained for the requested user(s).

At step 354, the location information for each requested user iscompared with the tracking information in the first user's request. Forexample, step 352 may include determining that location information isnot available for a requested user. Step 354 may include comparing thelocation information to quality of service (QoS) standards indicated bythe first user's request or profile information. For example, thelocation manager may compare an interest level for a particular user inthe tracking information with information indicating the quality of therequested location information or how long it has been since therequested location information was obtained. Step 354 may furtherinclude comparing the location information for each requested user withgeneral or default quality standards. For example, step 354 can includedetermining that the location information for a particular user isbeyond a threshold expiration period. Step 354 can also includeaccessing tracking information received from the remote users. Thetracking information can indicate that the remote user is not activelyutilizing location information, for example.

At step 356, it is determined whether the location information for eachrequested user meets all quality of service standards. If the locationinformation for each requested user meets the standards, a response isgenerated for the first user's message at step 358. The responseincludes the requested location information and optionally, profile orother information associated with the target users. For any locationinformation that was unavailable, the LSP provides an indication in oneembodiment.

If the location information for each requested user does not meet thequality of service standards at step 356, processing continues at step360. At step 360, the LSP issues a request to each mobile device forwhich the location information is not adequate. The request in oneexample is an instruction to the LSE at the client device to determine ahigh level accuracy location for the device and to return theinformation to the LSP. In another example, the request is simply anindication that a particular user is interested in the location of thetarget client device. For example, the LSP can pass the trackinginformation or a portion thereof to the remote client device that wasreceived from the first client device. The LSE at the target clientdevice can then determine how to respond. For example, the LSE maydetermine that the current location determination protocol is sufficientto respond or that the position engine should switch protocols so thatthe relative interest level can be satisfied. The LSE can access theposition engine and determine the required location information if notalready determined.

In one embodiment, step 360 includes issuing a push protocol message(e.g., a voice over internet protocol (VoIP) message) to the LSE at theclient device. For example, the LSE may register (e.g., with theoperating system) of the client device as a voice application. In thismanner, the operating system may pass incoming VoIP messages to the LSE.This can be beneficial in situations where the LSE is not active at thetarget client device, for example where the LSE is not activelyexecuting or has been placed into a background state by the operatingsystem. By enabling the LSE to respond to VoIP messages, the LSE can beactivated by the LSP even when the LSE is not currently executing at thetarget client device. Accordingly, one embodiment includes issuing aVoIP request to the target device at step 358 to activate the LSE at theclient device. In one embodiment, the VoIP request includes theinstruction to the LSE or the information for the LSE as describedabove. In another example, the LSE receives the VoIP request and inresponse, issues a request to the LSP. The LSP can receive the requestand respond with the instruction or the information described above. Inanother example, the step 360 includes responding to a periodic pollingrequest from the target mobile device.

At step 362, the location information from the target client device(s)is received. In one example, step 362 includes receiving a response tothe request issued at step 360. After receiving the locationinformation, processing continues at step 358 as described above withthe location information including any location information received atstep 362.

In one embodiment, the LSP does not compare the location information forthe tracked users against quality of service standards. The LSP accessesthe tracking information from each incoming request such as that of thefirst user at step 352. Any available location information can beprovided in response to the request with the tracking information. Thetracking information or an indication of the interest in a target useris automatically provided to the client device of the target user. TheLSP can determine from the tracking database or location databasewhether the target user's client device has sharing activated. Inanother example, the LSP can determine whether the target user's clientdevice has issued a request or other message to the LSP within athreshold period. If any of the conditions are met, the LSP can send amessage to the target client device so that updated location informationcan be received.

FIG. 5 is a flowchart describing processing at a client device in oneembodiment. In one example, FIG. 5 can be performed by a locationsharing engine at a client device as part of initiating a protocolchange at a client device, as may be performed as part of step 310 ofFIG. 3.

At step 402, the LSE determines the status of the power source for theclient device. Step 402 can include determining if the client device hasan unlimited, stable power source (e.g., plugged-in) or whether thepower source is limited, such as when the device is being powered by abattery. If the power source is limited, the LSE determines theremaining amount of power. If the power source is unlimited, the LSEsets the position engine to a high accuracy location protocol mode atstep 404. If the power source is limited and the remaining power is lessthan a threshold power level, the LSE sets the position engine to a lowaccuracy location protocol mode at step 406. It is noted that the LSEmay simply allow the position engine to remain in the appropriate modeat steps 404 and 406 and elsewhere as described.

If the power source is limited, but the remaining power is above thethreshold power level, the client device determines if location sharingis active at the client device at step 408. For example, step 408 caninclude determining if the location sharing engine is active (e.g.,executing) at the client device or whether the LSE has been placed inthe background (e.g., minimized or not currently executing). If the LSEis active at the client device, the LSE instructs the position engine tomaintain or initiate the high accuracy location protocol at step 410.

If location sharing is not active at the client device, the LSEdetermines whether there is interest in the location of the userassociated with the local client device at step 412. In one embodimentwhere the LSE is not active at the client device, steps 408 and 412 canbe performed in response to a message from the LSP or from anothermobile device. For example, the LSP may issue a VoIP message to the LSEafter receiving tracking information indicating that another user isinterested in the location of the local client device. The LSE mayrespond by issuing a request to the LSP for the tracking information tomake the determination at step 412. In another example, the VoIP messagemay contain the tracking information or a specific instruction withrespect to the illustrated decisions. In yet another example, the LSEmay register with the operating system to be notified when the locationof the client device changes. When the location changes, the LSE cansend an update to the LSP and in return receive any indication of userinterest from tracking information of those users.

If there is no interest in the user of the local client device, the LSEdetermines if the device is moving at step 414. If the device iscurrently moving, the LSE sets or maintains the position engine to thelow accuracy location protocol mode at step 416. If the device is notmoving, the LSE checks at step 418 for the accuracy of the last locationinformation determined for the local client device.

If the last location information was obtained using a high-accuracyprotocol, the client device sets the position engine to the low-accuracyprotocol mode at step 420. If the last location information was obtainedusing a low-accuracy protocol, the client device determines whether thelocal client device has been stationary for more than a threshold periodof time at step 422. If the client device has not been stationary formore than the threshold period, the LSE sets the position engine to thelow-accuracy protocol mode at step 424.

If the client device has been stationary for more than the thresholdperiod, the LSE sets the position engine to a high accuracy locationprotocol mode until at least one location fix is obtained at step 426.After the position fix is obtained at the high accuracy protocol, theposition engine is set to the low-accuracy protocol mode.

Returning to step 412, if there is interest in the user of the localclient device, the LSE determines at step 428 whether the requestinguser is more than a threshold distance from the current location of thelocal client device. If the requesting user is more than the thresholddistance from the local client device, the client device sets theposition engine to a high accuracy location protocol until at least onelocation fix is obtained at step 430. After the position fix is obtainedat the high accuracy protocol, the position engine is set to alow-accuracy protocol mode.

If the requesting user is not more than the threshold distance from theclient device, the LSE determines at step 432 whether the requestinguser is moving toward the local client device. If the user is not movingtoward the local client device, the LSE sets the position engine to ahigh accuracy location protocol until at least one location fix isobtained at step 434. After the position fix is obtained at the highaccuracy protocol, the position engine is set to a low-accuracyprotocol.

If the requesting user is moving toward the target client device, theclient device determines whether the position engine has been in a highaccuracy protocol for more than a threshold period of time at step 436.If the position engine has been in the high accuracy protocol for morethan the threshold period, the LSE sets the position engine to a lowaccuracy protocol for a predetermined period or amount of time at step440. If the position engine has not been in the high accuracy highaccuracy protocol for more than the threshold period, the LSE sets theposition engine to the high accuracy protocol at step 438.

FIG. 6 is a flowchart describing processing by a position engine tofacilitate different location determination protocols in response touser behavior or interest. In one example, the process of FIG. 6 can beperformed by the position engine in conjunction with the LSE of a clientdevice as shown in FIG. 5. In other examples, the position engine mayswitch protocols independently.

At step 502, the position engine determines if the location sharingengine has issued a mode command. If the LSE has issued a mode command,the position engine sets the indicated mode (e.g., high or low accuracy)at step 504. After setting the indicated mode or determining that nocommand has been received, the position engine determines theappropriate location protocol for the current mode at step 506. If thecurrent mode indicates a high-accuracy protocol, the position enginecompares the length of time since the last location determination with afirst threshold time period at step 508. If the length of time is lessthan the threshold period, processing returns to step 502 to determineif a mode command has been issued. If the length of time reaches thethreshold, the position engine determines location information for theclient device using a satellite positioning system or protocol at step510. In one example, the position engine accesses GPS circuitry at step510 to receive satellite positioning signals in order to obtain a highquality position fix. Step 510 may also include accessing the cellularor another RF transceiver to facilitate an A-GPS position fix at step510, for example.

If the current mode indicates a low-accuracy protocol at step 506, theposition engine compares the length of time since the last locationdetermination with a second threshold time period at step 512. In oneembodiment, the second threshold period used is longer than thethreshold period used for the low-accuracy protocol. In this manner, thehigh accuracy protocol can utilize a smaller interval between updates toprovide a more accurate representation of location. The lower accuracymode can utilize a larger interval to conserve battery power.

If the length of time is less than the second period, processing returnsto step 502. If the length of time is greater than the threshold, theposition engine determines location information for the client deviceusing a network-based position system at step 514. In one example, theposition engine accesses the cellular transceiver to determine theposition using a CGI process at step 514.

Accordingly, one embodiment includes a method of sharing locationinformation between computing devices that comprises determining firstlocation information for a first client device using a first locationprotocol, receiving tracking information associated with a second clientdevice, determining from the tracking information that the second clientdevice has indicated an interest in the location of the first clientdevice, and in response to the tracking information, determining secondlocation information for the first client device using a second locationprotocol, the second location protocol having a higher accuracy than thefirst location protocol.

A method of sharing location information between computing devices isprovided in one embodiment that comprises receiving at a server firsttracking information and first location information from a first clientdevice where the first location information is obtained using a firstlocation protocol, receiving at the server second location informationand second tracking information from a second client device where thesecond tracking information indicates a set of users being tracked atthe second client device, accessing profile information for the set ofusers and determining that the first client device is associated with auser in the set of users being tracked at the second client device,sending at least a portion of the second tracking information to thefirst client device to initiate a location determination protocol changeat the first client device, and receiving from the first client devicelocation information obtained at the first client device using a secondlocation protocol where the second location protocol has a higheraccuracy than the first location protocol.

A location sharing system in one embodiment comprises at least onestorage device and at least one location server in communication withthe at least one storage device. The at least one location server isconfigured to receive and store location information and trackinginformation associated with a plurality of subscribers, determine fromthe tracking information that a first subscriber has requested locationinformation for a second subscriber, determine a client deviceassociated with the second subscriber, and send at least a portion ofthe tracking information to the client device associated with the secondsubscriber to facilitate a change in location determination protocolbased on the tracking information indicating that the first subscriberhas requested location information for the second subscriber.

A mobile computing device in one embodiment comprises at least onetransceiver for communicating over one or more networks, satellitepositioning circuitry configured to receive satellite signals, and atleast one processor in communication with the at least one transceiverand the satellite positioning circuitry. The at least one processor isconfigured to receive tracking information associated with requests froma set of client computing devices for location information associatedwith the mobile computing device, determine location information for themobile computing device using the satellite positioning circuitry if thetracking information indicates a first interest in location informationassociated with the mobile computing device, and determine locationinformation for the mobile computing device using the at least onetransceiver if the tracking information indicates a second interest inlocation information associated with the mobile computing device.

A method of location sharing between mobile computing devices in oneembodiment comprises associating each of a plurality of users with atleast one of a plurality of mobile devices. The plurality of usersinclude a first user associated with a first mobile device. The methodfurther comprises determining whether information has been received fromany of the plurality of mobile devices indicating that a currentlocation of the first user is being used at one of the plurality ofmobile devices, if information has been received indicating that acurrent location of the first user is being used, determining locationinformation of the first mobile device at a first accuracy level, and ifinformation has not been received indicating that a current location ofthe first user is being used, determining location information of thefirst mobile device at a second accuracy level. The first accuracy levelis higher than the second accuracy level.

One embodiment includes a method performed as part of a location sharingapplication at a first mobile device. The first mobile device includes aglobal positioning system (GPS) processor for determining a location ofthe first mobile device and at least one additional processor fordetermining the location of the first mobile device. The methodcomprises determining the location of the first mobile and activatingthe GPS processor for determining the location of the first mobiledevice based on whether the location of the first mobile device is beingaccessed at a second mobile device.

FIG. 7 is a high level block diagram of a computing system which can beused to implement any of the computing devices of FIGS. 1 and 2. Thecomputing system of FIG. 7 includes processor 80, memory 82, massstorage device 84, peripherals 86, output devices 88, input devices 90,portable storage 92, and display system 94. For purposes of simplicity,the components shown in FIG. 7 are depicted as being connected via asingle bus 96. However, the components may be connected through one ormore data transport means. In one alternative, processor 80 and memory82 may be connected via a local microprocessor bus, and the mass storagedevice 84, peripheral device 86, portable storage 92 and display system94 may be connected via one or more input/output buses.

Processor 80 may contain a single microprocessor, or may contain aplurality of microprocessors for configuring the computer system as amultiprocessor system. Memory 82 stores instructions and data forprogramming processor 80 to implement the technology described herein.In one embodiment, memory 82 may include banks of dynamic random accessmemory, high speed cache memory, flash memory, other nonvolatile memory,and/or other storage elements. Mass storage device 84, which may beimplemented with a magnetic disc drive or optical disc drive, is anonvolatile storage device for storing data and code. In one embodiment,mass storage device 84 stores the system software that programsprocessor 80 to implement the technology described herein. Portablestorage device 92 operates in conjunction with a portable nonvolatilestorage medium, such as a floppy disc, CD-RW, flash memory card/drive,etc., to input and output data and code to and from the computing systemof FIG. 7. In one embodiment, system software for implementingembodiments is stored on such a portable medium, and is input to thecomputer system via portable storage medium drive 92.

Peripheral devices 86 may include any type of computer support device,such as an input/output interface, to add additional functionality tothe computer system. For example, peripheral devices 86 may include oneor more network interfaces for connecting the computer system to one ormore networks, a modem, a router, a wireless communication device, etc.Input devices 90 provide a portion of a user interface, and may includea keyboard or pointing device (e.g. mouse, track ball, etc.). In orderto display textual and graphical information, the computing system ofFIG. 7 will (optionally) have an output display system 94, which mayinclude a video card and monitor. Output devices 88 can includespeakers, printers, network interfaces, etc. Device 100 may also containcommunications connection(s) 112 that allow the device to communicatewith other devices via a wired or wireless network. Examples ofcommunications connections include network cards for LAN connections,wireless networking cards, modems, etc. The communication connection(s)can include hardware and/or software that enables communication usingsuch protocols as DNS, TCP/IP, UDP/IP, and HTTP/HTTPS, among others.

The components depicted in the computing system of FIG. 7 are thosetypically found in computing systems suitable for use with thetechnology described herein, and are intended to represent a broadcategory of such computer components that are well known in the art.Many different bus configurations, network platforms, operating systemscan be used. The technology described herein is not limited to anyparticular computing system.

The technology described herein, including the various engines andmanagers, can be implemented using hardware, software, or a combinationof both hardware and software. The software used is stored on one ormore of the processor readable storage devices described above (e.g,memory 82, mass storage 84 or portable storage 92) to program one ormore of the processors to perform the functions described herein. Theprocessor readable storage devices can include non-transitory, tangiblecomputer readable media such as volatile and non-volatile media,removable and non-removable media. Tangible computer readable media maybe implemented in any method or technology for storage of informationsuch as computer readable instructions, data structures, program modulesor other data. Examples of tangible computer readable media include RAM,ROM, EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other non-transitory, tangible medium which can be used to storethe desired information and which can be accessed by a computer. Inalternative embodiments, some or all of the software can be replaced bydedicated hardware including custom integrated circuits, gate arrays,FPGAs, PLDs, and special purpose computers. In one embodiment, software(stored on a storage device) implementing one or more embodiments isused to program one or more processors. The one or more processors canbe in communication with one or more tangible computer readablemedia/storage devices, peripherals and/or communication interfaces. Inalternative embodiments, some or all of the software can be replaced bydedicated hardware including custom integrated circuits, gate arrays,FPGAs, PLDs, and special purpose computers.

The foregoing detailed description has been presented for purposes ofillustration and description. It is not intended to be exhaustive or tolimit the invention to the precise form disclosed. Many modificationsand variations are possible in light of the above teachings. Thedescribed embodiments were chosen in order to best explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto.

What is claimed is:
 1. A method of sharing location information betweencomputing devices, comprising: receiving at a server first trackinginformation and first location information from a first client device,the first location information being obtained using a first locationprotocol; receiving at the server second location information and secondtracking information from a second client device, the second trackinginformation indicating a set of users being tracked at the second clientdevice; accessing profile information for the set of users anddetermining that the first client device is associated with a user inthe set of users being tracked at the second client device; sending atleast a portion of the second tracking information to the first clientdevice to initiate a location determination protocol change at the firstclient device; and receiving from the first client device locationinformation obtained at the first client device using a second locationprotocol, the second location protocol having a higher accuracy than thefirst location protocol.
 2. A method according to claim 1, whereinsending at least a portion of the second tracking information comprisessending information indicating an interest at the second client devicefor location information of the user.
 3. A method according to claim 1,further comprising: determining that location sharing is not active atthe first client device; and sending a voice over internet protocolmessage to the first client device in response to determining thatlocation sharing is not active, the voice over internet protocol messageactivating location sharing at the first client device; receiving fromthe first client device a request for location sharing information aftersending the voice over internet protocol message; wherein the at least aportion of the tracking information from the second client device issent to the first client device in response to the request from thefirst client device.
 4. A method according to claim 3, whereindetermining that location sharing is not active at the first clientdevice, comprises: determining that location information or trackinginformation for the client device at a location sharing server is olderthan a threshold period.
 5. A method according to claim 4, whereindetermining that location sharing is not active at the first clientdevice, comprises: determining that the first client device has notissued a request for location sharing information to a location sharingserver within a threshold time period.
 6. A location sharing system,comprising: at least one storage device; at least one location server incommunication with the at least one storage device, the at least onelocation server is configured to: receive and store location informationand tracking information associated with a plurality of subscribers;determine from the tracking information that a first subscriber hasrequested location information for a second subscriber; determine aclient device associated with the second subscriber; and send at least aportion of the tracking information to the client device associated withthe second subscriber to facilitate a change in location determinationprotocol based on the tracking information indicating that the firstsubscriber has requested location information for the second subscriber.7. A location sharing system according to claim 6, wherein the at leastone location server is configured to: determine whether location sharingis active at the client device based on the location information and thetracking information; if location sharing is not active at the clientdevice, sending a voice over internet protocol message to the clientdevice; and receiving from the first client device a request forlocation sharing information after sending the voice over internetprotocol message; wherein the at least a portion of the trackinginformation is sent to the first client device in response to therequest from the first client device.
 8. A location sharing systemaccording to claim 6, wherein the at least one location server isconfigured to: determine from at least one of the tracking informationand the location information that the client device is operating in alow-accuracy location protocol mode; wherein the at least a portion ofthe tracking information is sent to the client device based ondetermining that the client device is operating in the low-accuracylocation protocol mode and the tracking information indicating that thefirst subscriber has requested location information for the secondsubscriber.
 9. A mobile computing device, comprising: at least onetransceiver for communicating over one or more networks; satellitepositioning circuitry configured to receive satellite signals; at leastone processor in communication with the at least one transceiver and thesatellite positioning circuitry, the at least one processor isconfigured to: receive tracking information associated with requestsfrom a set of client computing devices for location informationassociated with the mobile computing device; determine locationinformation for the mobile computing device using the satellitepositioning circuitry if the tracking information indicates a firstinterest in location information associated with the mobile computingdevice; and determine location information for the mobile computingdevice using the at least one transceiver if the tracking informationindicates a second interest in location information associated with themobile computing device.
 10. A mobile computing device according toclaim 9, wherein the at least one processor is configured to: determinefrom the tracking information whether any client devices in the set ofclient devices are actively requesting location information associatedwith the mobile computing device; for any client device requestinglocation information associated with the mobile computing device,determining whether the client device is more than a threshold distancefrom the mobile computing device; if said any client device is more thanthe threshold distance from the mobile computing device, determiningthat the tracking information indicates the first interest; and if saidany client device is not more than the threshold distance from themobile computing device, determining that the tracking informationindicates the second interest.
 11. A mobile computing device accordingto claim 9, wherein: the tracking information indicates a first interestwhen one or more of the client computing devices have provided trackinginformation indicating interest in a user associated with the mobilecomputing device.
 12. A mobile computing device according to claim 11,wherein: the tracking information indicates a second interest when theset of client computing devices have not provided tracking informationindicating interest in a user associated with the mobile computingdevice.
 13. A mobile computing device according to claim 11, wherein:the first interest is a first level of interest in the locationinformation of the user associated with the mobile computing device; andthe tracking information indicates a second interest when one or more ofthe client computing devices have provided tracking informationindicating a second level of interest in a user associated with themobile computing device.
 14. A method of location sharing between mobilecomputing devices, the method comprising: associating each of aplurality of users with at least one of a plurality of mobile devices,the plurality of users including a first user associated with a firstmobile device; determining whether information has been received fromany of the plurality of mobile devices indicating that a currentlocation of the first user is being used at one of the plurality ofmobile devices; if information has been received indicating that acurrent location of the first user is being used, determining locationinformation of the first mobile device at a first accuracy level; and ifinformation has not been received indicating that a current location ofthe first user is being used, determining location information of thefirst mobile device at a second accuracy level, the first accuracy levelbeing higher than the second accuracy level.
 15. A method according toclaim 14, wherein: the information indicates whether the currentlocation of the first user is being displayed or has recently beendisplayed at one of the plurality of mobile devices.
 16. A methodaccording to claim 14, wherein: determining location information of thefirst mobile device at a first accuracy level comprises receiving at afirst server the location information at the first accuracy level fromthe first mobile device; and determining location information of thefirst mobile device at a second accuracy level comprises receiving atthe first server the location information at the second accuracy levelfrom the first mobile device.
 17. A method according to claim 16,wherein: determining location information of the first mobile device ata first accuracy level comprises sending a first instruction from thefirst server to the first mobile device to determine the locationinformation at the first accuracy level; and determining locationinformation of the first mobile device at a second accuracy levelcomprises sending a second instruction from the first server to thefirst mobile device to determine the location information at the secondaccuracy level.
 18. A method according to claim 17, wherein: the firstinstruction causes the first mobile device to determine the locationinformation using a first location determination mechanism on the firstmobile device; and the second instruction causes the first mobile deviceto determine the location information using a second locationdetermination mechanism on the first mobile device.
 19. A methodaccording to claim 18, wherein: the first location determinationmechanism includes a GPS receiver; and the second location determinationmechanism includes a cellular identification mechanism.
 20. A methodperformed as part of a location sharing application at a first mobiledevice, the first mobile device including a global positioning system(GPS) processor for determining a location of the first mobile deviceand at least one additional processor for determining the location ofthe first mobile device: determining the location of the first mobiledevice and reporting the location to at least one remote applicationserver; and activating the GPS processor for determining the location ofthe first mobile device based on whether the location of the firstmobile device is being accessed at the second mobile device.
 21. Amethod according to claim 20, wherein activating the GPS processor basedon whether the location of the first mobile device is being accessed atthe second mobile device includes: receiving information from the firstapplication server indicating whether the location of the mobile deviceis being accessed at the second mobile device; determining whether alocation of the second mobile device is greater than a thresholddistance away from the first mobile device; and activating the GPSprocessor based on whether the second mobile device is greater than thethreshold distance from the first mobile device if the informationindicates the location of the mobile device is being accessed at thesecond mobile device.
 22. A method according to claim 21, whereinactivating the GPS processor based on whether the location of the firstmobile device is being accessed at the second mobile device includes:activating the GPS processor based on whether the second mobile deviceis moving toward the first mobile device if the second mobile device isnot more than the threshold distance from the first mobile device.
 23. Amethod according to claim 22, wherein activating the GPS processor basedon whether the location of the first mobile device is being accessed atthe second mobile device includes: activating the GPS processor if thesecond mobile device is moving toward the first mobile device and thefirst mobile device has not been in a high accuracy mode correspondingto the GPS processor for more than a threshold period.